1. Field
The present disclosure relates generally to antennas and, in particular, to phased array antennas. Still more particularly, the present disclosure relates to a method and apparatus for processing signals in waveguides for antennas.
2. Background
A phased array antenna is an antenna comprised of antenna elements. Each of the antenna elements can radiate electromagnetic signals or detect electromagnetic signals. Each of the antenna elements may be associated with a phase shifter. The elements in a phased array antenna may emit electromagnetic signals to form a beam that can be steered at different angles. The beam may be emitted normal to the surface of the elements radiating the radio electromagnetic signals. Through controlling the manner in which the signals are emitted, the direction may be changed. The changing of the direction is also referred to as steering. For example, many phased array antennas may be controlled to direct a beam at an angle of about 60 degrees from a normal direction from the arrays in the antenna.
Phased array antennas have many uses. For example, phased array antennas may be used in broadcasting amplitude modulated and frequency modulated signals for various communications systems, such as airplanes, ships, and satellites. As another example, phased array antennas are commonly used with seagoing vessels, such as warships, for radar systems. Phased array antennas allow a warship to use one radar system for surface detection and tracking, air detection and tracking, and missile uplink capabilities. Further, phased array antennas may be used to control missiles during the course of the missile's flight.
Phased array antennas also are commonly used to provide communications between various vehicles. Phased array antennas are used in communications with spacecraft. As another example, phased array antennas may be used on a moving vehicle or seagoing vessel to communicate with an aircraft.
A phased array antenna is typically comprised of a transmitter and a receiver array. During operation, either element may encounter interference from spurious external sources or from the different elements making up the phased array antenna.
For example, an antenna transmitting a signal may couple microwave energy into an antenna receiving signals. As another example, other sources of electromagnetic signals may have frequencies that may couple or cause the electromagnetic signals to couple back into the antenna transmitting signals. Further, the antennas receiving the signals may receive frequencies of electromagnetic signals that are picked up from the antennas transmitting signals in the phased array antenna.
Currently, band pass filters and band stop filters may be used to reduce unwanted signals. These types of filters may be placed within the waveguides for the different antenna elements. These types of filters, however, may require larger sizes than desired for the waveguides.
Therefore, it would be advantageous to have a method and apparatus that takes into account one or more of the issues discussed above, as well as possibly other issues.